Electronic endoscope apparatuses have been widely used for observation and diagnosis for a body cavity. The electronic endoscope apparatus includes an image pick-up device at its tip portion, and includes an electronic endoscope which outputs an image signal of an image shot by the image pick-up device, and a processor for the electronic endoscope which processes the image signal from the electronic endoscope, converts the image signal into a video signal having a predetermined format (e.g., a video signal in NTSC format) and displays the video, for example, on a monitor.
Generally, the processor for the electronic endo scope displays the image picked up by the electronic endoscope on the monitor as a moving image. Further, the processor for the electronic endo scope has the function of displaying the picked up image as a still image in order to make it possible to more specifically observe an observation target portion.
Displaying of the still image is triggered, for example, upon detection of pressing of an operation button provided on the electronic endoscope or the processor for the electronic endoscope. That is, a frame displayed on a monitor when the operation button is pressed or a next frame is continued to be displayed as a still image.
In the above described configuration, a user of the electronic endoscope is required to press the operation button at an appropriate timing while checking the moving image displayed on the monitor. However, since it is necessary to operate the electronic endoscope and press the operation button while checking the monitor, it is not easy to obtain a desired still image due to delay of the pressing timing of the operation button. For example, when the operation button is pressed while the observation target portion is moving, a problem arises that a blurry still image or a still image affected by color drift is obtained.
In order to prevent occurrence of a blurry image or a still image affected by color drift, a processor for an electronic endoscope having the function described in Japanese Patent Publication No. JP3497231B (hereafter, referred to as patent document 1) has been proposed. The processor for the electronic endoscope described in patent document 1 is configured to store image data of a plurality of latest frames in a memory, and when an operation for obtaining a still image (e.g., pressing of an operation button) is performed, the processor selects an image having a lower level of blur or color drift and displayed the selected image as a still image on the monitor.